(R Igraph) Using affilliation to create subgraph from adjacency matrix

Question

I need to create a subgraph from an adjacency matrix selecting by affiliation data. How do I match an adjacency and an affiliation matrix?

Take the following adjacency matrix:

    A   B   C   D   E   F   G
A   0   1   0   1   0   1   0
B   1   0   1   1   0   1   0
C   0   1   0   0   0   0   0
D   1   1   0   0   1   1   0
E   0   0   0   1   0   1   0
F   1   1   0   1   1   0   1
G   0   0   0   0   0   1   0

And the following affiliation matrix:

    P   R   Q
A   1   1   0
B   1   0   1
C   1   1   0
D   0   1   0
E   1   0   1
F   0   0   1
G   1   1   0

How do I create a subgraph from the adjacency matrix only with the nodes corresponding to P in the affiliation matrix?

Answer 1

If your goal is to:

• filter out nodes from your adjacency matrix where the corresponding P is 1 in the affiliation matrix
• convert filtered adjacency matrix to an igraph object

then you can accomplish that with the following:

# the names(which()) isn't needed for the subset of adj
p_nodes <- names(which(aff[,"P"] == 1))
p_adj   <- adj[p_nodes, p_nodes]

p_graph <- igraph::graph.adjacency(p_graph)